1. Field of the Invention
The present invention relates to a valve device used as, for example, a pneumatic controller or a stopper for a gas tank.
2. Description of the Related Art
For example, known as a valve device that operates under a high-pressure condition is a device including: a main valve body that opens and closes a main passage formed at a housing; and a pilot valve body that controls opening/closing operations of the main valve body. For example, Japanese Laid-Open Patent Application Publication No. 2008-232440 discloses a valve device in which a main valve body and a pilot valve body are arranged coaxially.
FIG. 6 shows a part of a valve device 100 disclosed in Japanese Laid-Open Patent Application Publication No. 2008-232440. In the valve device 100, a main valve body 120 performs an opening operation by an electromagnetic force generated by a current flowing through a solenoid portion (not shown) and performs a closing operation by a biasing force of a spring 150. Even in a case where a pressure difference between primary pressure P1 that is pressure of a primary passage 111 of a main passage 110 and secondary pressure P2 that is pressure of a secondary passage 112 is large, a pilot valve body 130 realizes the opening operation of the main valve body 120 by a low electromagnetic force.
Specifically, one end portion of the pilot valve body 130 is coupled to a movable core, and the other end portion of the pilot valve body 130 is coupled to the main valve body 120 via a pin 140. The pin 140 is inserted into a loose-fit hole 131 formed at the other end portion of the pilot valve body 130. When the current flows through the solenoid portion, the pilot valve body 130 first moves away from the main valve body 120 by a gap between the loose-fit hole 131 and the pin 140. With this, a communication passage 140 formed at the main valve body 120 opens, so that the primary passage 111 and the secondary passage 112 communicate with each other. After that, when the pressure difference between the primary pressure P1 and the secondary pressure P2 becomes small, the main valve body 120 performs the opening operation by the electromagnetic force of the solenoid portion.
However, according to the above mechanism in which the main valve body 120 performs the opening operation after the pressure difference between the primary pressure P1 and the secondary pressure P2 is reduced, in a case where a compression volume at a downstream side of the valve device 100 is large, a time (that is, a response time) from when the current starts flowing through the solenoid portion until when the main valve body 120 performs the opening operation may become long. In contrast, a so-called differential pressure-driven valve device 200 disclosed in U.S. Pat. No. 7,309,113 and shown in FIG. 7 has excellent responsiveness, the valve device 200 causing a main valve body 220 to perform the opening operation by a pressure difference acting on the main valve body 220.
Specifically, in the valve device 200, a spring chamber 230 in which a spring 240 that biases the main valve body 220 in a closing operation direction is provided communicates with a tank inner space where a primary passage 211 of a main passage 210 opens, via a first pilot passage 251 and also communicates with a second pilot passage 252. A restrictor is provided at the pilot passage 251. The second pilot passage 252 is opened and closed by a pilot valve body 265. When the pilot valve body 265 opens, the second pilot passage 252 communicates with a secondary passage 212 of the main passage 210. When the second pilot passage 252 is being closed by the pilot valve body 265, pressure P3 of the spring chamber 230 is equal to the primary pressure P1. In contrast, when the pilot valve body 265 performs the opening operation by a current flowing through a solenoid portion 260, the pressure P3 of the spring chamber 230 becomes lower than the primary pressure P1 and higher than the secondary pressure P2. Thus, the main valve body 220 performs the opening operation.